Being able to effectively introduce foreign molecules, such as DNA, siRNA, protein, etc., into biological cells is of great importance in biology and biotechnology. Particularly effective transfection of biological cells with nucleic acid molecules is an essential prerequisite in elucidating how genes function in complex cellular context and how their activities could be modulated for therapeutic intervention. Cell transfection is routinely used in fundamental biology research and pharmaceutical development. Traditionally studies are normally carried out on a low throughput gene-by-gene scale, which has created a huge bottleneck in functional genomic study and drug discovery. Development of high-throughput cell transfection technology will permit functional analysis of massive number of genes and how their activities could be modulated by chemical or biological entities. Development of high-throughput cell transfection methods will significantly accelerate biology research and facilitate translation of genomic knowledge into therapeutic means in fighting various diseases.
Several methods are currently available for cell transfection, such as viral transduction, lipofection, electroporation, etc. Recombinant vectors derived from viruses are very effective in transfecting engineered cell lines and primary cells. However, use of viral vectors often results in undesirable alteration of cellular functions, in addition vector preparation is time-consuming and laborious, thus its application in high-throughput transfection is limited. Lipid based transfection methods are routinely used in high-throughput transfection applications, and a recent invention based on lipid transfection claims ultra-high-throughput capability [U.S. Pat. No. 6,544,790]. Nevertheless, all lipofection methods lack of ability of transfection non-dividing cells, particularly primary cells directly derived from animal tissue.
Electroporation is a process associated with transient permeabilization of cell membranes under electrical fields. It has been shown to be capable of delivering various substances (genes, siRNAs, antibodies, proteins and nanoparticles) into virtually any type of cells (engineered cell lines and primary cells). On the other hand, electroporation is often known for low efficiency, poor inconsistency, and extensive cell damage. This is largely due to the trial-and-error approach adopted by conventional electroporation systems, which apply hundreds to thousands of volts to cells suspended in solution, inevitably kill large portion of cells due to a process called irreversible electroporation.
Several novel methods and devices have been invented recently to address issues of low transfection efficiency and poor cell motility associated with electroporation[U.S. Pat. No. 6,300,108, U.S. Pat. No. 6,403,348, US2005/0170510]. The related arts employ feed-back mechanisms to monitor electroporation in cells so to achieve high degree of transfection efficiency and high cell motility. The new methods and devices have been proven to be very useful in transfection of cells with a variety of foreign molecules. However, the design of the devices limit their capability of processing cells in high-throughput fashion, which is particularly required by cell-based assays for functional genomics study and drug discovery. Secondly, in the case of transfecting cells with DNA molecules, the related arts do not address effective delivery of DNA molecules into cell nuclei, which is required for cells to express proteins encoded by the DNA molecules. These and other needs are addressed by the transfection devices of the present invention. In addition, novel use of the disclosed transfection devices and methods in cell-based assays employing transient transfection is also presented in this invention.